1. Field of the Invention
This invention relates to an optical information medium on which it is possible to print, by use of a printing ink, on a side thereof which is opposite to a side through which reproduction light is passed.
2. Description of the Prior Art
In fields such as audio and information processings, an optical information medium called a compact disk (hereinafter referred to simply as CD) has now been in wide use. The CD has such a structure which has a substrate in the form of a doughnut-shaped disk made, for example, of polycarbonates, and a reflective layer of gold or aluminium vacuum deposited on the substrate. A protective layer, such as of a UV-cured resin, is formed on the reflective layer. Information data are encoded by forming projected and recessed pits on or in the surface of the substrate according to a spiral arrangement. Simultaneously with the formation of the substrate, these pits have been formed using molds such as stampers. The reflective layer is then formed on the pits-bearing substrate. When fabricated, the CD has already had the data encoded therein and can be thus used as a read-only optical information medium.
The usual practice is that the CD has an index indicating a recorded content and a variety of designs printed on the surface of the protective layer with use of a UV-curable or oil ink. These prints have been usually made by a printing means or procedure using transfer from a printing plate, such as screen printing, tampon printing or offset printing. These printing procedures are ones which are particularly suitable for so-called mass printing wherein the same pattern is printed in a great numbers at one time.
On the other hand, musical performances by amateur players have recently become popular. As a wide variety of amateur players are being taken part in such performances, it has become full of activities that amateur players individually make a relatively small number of CDs of their own work. These CD articles are created for the purposes, for example, of promotion, audition, test and setting up on their own expenses. Especially, because write-once optical information mediums which are so-called CD-WO and in which information can be written once by use of a laser beam and reproduced with use of a CD player, have now been developed, such a self-made CD can be made more readily. Alternatively, in the field of computers, so-called CD-ROMs have become popular. As the write-once optical information medium has spread, users have now started to set up CD-ROM using CD-WO.
The protective layer of the optical information medium such as the thus self-made CD has no statement thereon, or has general letters or patterns alone printed thereon by means of a UV-curable ink or oil ink. It is thus necessary to indicate the index of a record content and, if necessary, other designs, on the surface of the protective layer or the printed surface of a label prior to or after recording of private information on the optical information medium.
However, the afore-mentioned printing procedure or means is used to print during the course of the fabrication process of the medium after formation of the protective layer. Since both protective layer surface and print surface are hydrophobic in nature, excessive equipment becomes necessary in order to print the protective layer on the surface thereof after recording of the private information. This eventually makes it difficult to arbitrarily print personal and optionally desired information. Accordingly, it is usual to write on the surface of the protective layer by use of an oily felt tipped pen or to attach a label on the surface. However, this requires hand-writing one at a time, thus being troublesome. In addition, the written patterns or their quality will not be made uniform and have a bad appearance, thus presenting the problem that the self-made optical information medium does not have a good appearance as a whole. Especially, where a label is attached, the surface is raised by the thickness of the attached label, leading to the problem that the optical information medium will undesirably undergo eccentric revolutions or surface fluctuation when reproduced and followed up.